The present invention is directed to phase change (hot melt) ink compositions. More specifically, the present invention is directed to phase change ink compositions suitable for use in ink jet printing processes, including piezoelectric ink jet printing processes, acoustic ink jet printing processes, and the like. One embodiment of the present invention is directed to a phase change ink composition comprising a colorant and an ink vehicle, said ink being a solid at temperatures less than about 50° C. and exhibiting a viscosity of no more than about 20 centipoise at a jetting temperature of no more than about 160° C., wherein the ink vehicle comprises (1) a material selected from (a) those of the formulaW—C(b) those of the formulaC1—X—C2(c) those of the formula (d) those of the formula or (e) mixtures of two or more of (a), (b), (c), and/or (d); or (2) a material selected from mixtures of (a) at least one member selected from (i) those of the formulaW1—A(ii) those of the formulaA1—X—A2(iii) those of the formula (iv) those of the formula (v) those of the formulaA1—X—B1(vi) those of the formula (vii) those of the formula (viii) those of the formula or (ix) mixtures of two or more of (i), (ii), (iii), (iv), (v), (vi), (vii), and/or (viii), and (b) at least one member selected from (i) those of the formulaW2—B(ii) those of the formulaB1—X2—B2(iii) those of the formula (iv) those of the formula (v) those of the formulaA2—X2—B2(vi) those of the formula (vii) those of the formula (viii) those of the formula or (ix) mixtures of two or more of (i), (ii), (iii), (iv), (v), (vi), (vii), and/or (viii), wherein each “A” is an acidic moiety and each “B” is a basic moiety, wherein each “A” is capable of forming at least one hydrogen bond with at least one “B” and each “B” is capable of forming at least one hydrogen bond with at least one “A”, each “C” is a moiety either capable of forming at least one hydrogen bond with a moiety identical to itself or capable of forming at least one hydrogen bond with another “C” moiety, each “W” is a monovalent moiety, each “X” is a divalent moiety, each “Y” is a trivalent moiety, and each “Z” is a tetravalent moiety, wherein at a first temperature hydrogen bonds of sufficient strength exist either between the “A” groups and the “B” groups or between the “C” groups so that the ink vehicle forms hydrogen-bonded dimers, oligomers, or polymers, and wherein at a second temperature which is higher than the first temperature the hydrogen bonds either between the “A” groups and the “B” groups or between the “C” groups are sufficiently broken that fewer hydrogen-bonded dimers, oligomers, or polymers are present in the ink at the second temperature than are present in the ink at the first temperature, so that the viscosity of the ink at the second temperature is lower than the viscosity of the ink at the first temperature.
Ink jet printing processes that employ inks that are solid at room temperature and liquid at elevated temperatures are known. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing solid inks for printing on a substrate such as paper. The ink vehicle is chosen to have a melting point above room temperature so that the ink, which is melted in the apparatus, will not be subject to evaporation or spillage during periods of nonprinting. The vehicle selected possesses a low critical temperature to permit the use of the solid ink in a thermal ink jet printer. In thermal ink jet printing processes employing these phase change inks, the solid ink is melted by a heater in the printing apparatus and used as a liquid in a manner similar to that of conventional piezoelectric or thermal ink jet printing. Upon contact with the printing substrate, the molten ink solidifies rapidly, enabling the dye to remain on the surface instead of being carried into the paper by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. After the phase change ink is applied to the substrate, freezing on the substrate resolidifies the ink.
Acoustic ink jet printing processes are known. In acoustic ink jet printing processes, an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface (i.e., liquid/air interface) of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. These principles have been applied to prior ink jet and acoustic printing proposals. For example, K. A. Krause, “Focusing Ink Jet Head,” IBM Technical Disclosure Bulletin, Vol. 16, No. 4, September 1973, pp. 1168-1170, the disclosure of which is totally incorporated herein by reference, describes an ink jet in which an acoustic beam emanating from a concave surface and confined by a conical aperture was used to propel ink droplets out through a small ejection orifice. Acoustic ink printers typically comprise one or more acoustic radiators for illuminating the free surface of a pool of liquid ink with respective acoustic beams. Each of these beams usually is brought to focus at or near the surface of the reservoir (i.e., the liquid/air interface). Furthermore, printing conventionally is performed by independently modulating the excitation of the acoustic radiators in accordance with the input data samples for the image that is to be printed. This modulation enables the radiation pressure which each of the beams exerts against the free ink surface to make brief, controlled excursions to a sufficiently high pressure level for overcoming the restraining force of surface tension. That, in turn, causes individual droplets of ink to be ejected from the free ink surface on demand at an adequate velocity to cause them to deposit in an image configuration on a nearby recording medium. The acoustic beam may be intensity modulated or focused/defocused to control the ejection timing, or an external source may be used to extract droplets from the acoustically excited liquid on the surface of the pool on demand. Regardless of the timing mechanism employed, the size of the ejected droplets is determined by the waist diameter of the focused acoustic beam. Acoustic ink printing is attractive because it does not require the nozzles or the small ejection orifices which have caused many of the reliability and pixel placement accuracy problems that conventional drop on demand and continuous stream ink jet printers have suffered. The size of the ejection orifice is a critical design parameter of an ink jet because it determines the size of the droplets of ink that the jet ejects. As a result, the size of the ejection orifice cannot be increased, without sacrificing resolution. Acoustic printing has increased intrinsic reliability because there are no nozzles to clog. As will be appreciated, the elimination of the clogged nozzle failure mode is especially relevant to the reliability of large arrays of ink ejectors, such as page width arrays comprising several thousand separate ejectors. Furthermore, small ejection orifices are avoided, so acoustic printing can be performed with a greater variety of inks than conventional ink jet printing, including inks having higher viscosities and inks containing pigments and other particulate components. It has been found that acoustic ink printers embodying printheads comprising acoustically illuminated spherical focusing lenses can print precisely positioned pixels (i.e., picture elements) at resolutions which are sufficient for high quality printing of relatively complex images. It has also been discovered that the size of the individual pixels printed by such a printer can be varied over a significant range during operation, thereby accommodating, for example, the printing of variably shaded images. Furthermore, the known droplet ejector technology can be adapted to a variety of printhead configurations, including (1) single ejector embodiments for raster scan printing, (2) matrix configured ejector arrays for matrix printing, and (3) several different types of pagewidth ejector arrays, ranging from single row, sparse arrays for hybrid forms of parallel/serial printing to multiple row staggered arrays with individual ejectors for each of the pixel positions or addresses within a pagewidth image field (i.e., single ejector/pixel/line) for ordinary line printing. Inks suitable for acoustic ink jet printing typically are liquid at ambient temperatures (i.e., about 25° C.), but in other embodiments the ink is in a solid state at ambient temperatures and provision is made for liquefying the ink by heating or any other suitable method prior to introduction of the ink into the printhead. Images of two or more colors can be generated by several methods, including by processes wherein a single printhead launches acoustic waves into pools of different colored inks. Further information regarding acoustic ink jet printing apparatus and processes is disclosed in, for example, U.S. Pat. Nos. 4,308,547, 4,697,195, 5,028,937, 5,041,849, 4,751,529, 4,751,530, 4,751,534, 4,801,953, and 4,797,693, the disclosures of each of which are totally incorporated herein by reference. The use of focused acoustic beams to eject droplets of controlled diameter and velocity from a free-liquid surface is also described in J. Appl. Phys., vol. 65, no. 9 (May 1, 1989) and references therein, the disclosure of which is totally incorporated herein by reference.
In acoustic ink printing processes, the printhead produces approximately 2.2 picoliter droplets by an acoustic energy process. The ink under these conditions preferably displays a melt viscosity of from about 1 to about 25 centipoise at the jetting temperature. In addition, once the ink has been jetted onto the printing substrate, the image thus generated preferably exhibits excellent crease properties, and is nonsmearing, waterfast, of excellent transparency, and of excellent fix. The vehicle preferably displays a low melt viscosity in the acoustic head while also displaying solid like properties after being jetted onto the substrate Since the acoustic head can tolerate temperatures typically up to about 180° C., the vehicle for the ink preferably displays liquid-like properties (such as a viscosity of from about 1 to about 25 centipoise) at a temperature of from about 75 to about 180° C., and solidifies or hardens after being jetted onto the substrate.
The use of phase change inks in acoustic ink printing processes is also known. U.S. Pat. No. 4,745,419 (Quate et al.), the disclosure of which is totally incorporated herein by reference, discloses acoustic ink printers of the type having a printhead including one or more acoustic droplet ejectors for supplying focused acoustic beams. The printer comprises a carrier for transporting a generally uniformly thick film of hot melt ink across its printhead, together with a heating means for liquefying the ink as it nears the printhead. The droplet ejector or ejectors are acoustically coupled to the ink via the carrier, and their output focal plane is essentially coplanar with the free surface of the liquefied ink, thereby enabling them to eject individual droplets of ink therefrom on command. The ink, on the other hand, is moved across the printhead at a sufficiently high rate to maintain the free surface which it presents to the printhead at a substantially constant level. A variety of carriers may be employed, including thin plastic and metallic belts and webs, and the free surface of the ink may be completely exposed or it may be partially covered by a mesh or perforated layer. A separate heating element may be provided for liquefying the ink, or the lower surface of the carrier may be coated with a thin layer of electrically resistive material for liquefying the ink by localized resistive heating.
U.S. Pat. No. 5,541,627 (Quate), the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus for ejecting droplets from the crests of capillary waves riding on the free surface of a liquid by parametrically pumping the capillary waves with electric fields from probes located near the crests. Crest stabilizers are beneficially used to fix the spatial locations of the capillary wave crests near the probes. The probes are beneficially switchably connected to an AC voltage supply having an output that is synchronized with the crest motion. When the AC voltage is applied to the probes, the resulting electric field adds sufficient energy to the system so that the surface tension of the liquid is overcome and a droplet is ejected. The AC voltage is synchronized such that the droplet is ejected about when the electric field is near is minimum value. A plurality of droplet ejectors are arranged and the AC voltage is switchably applied so that ejected droplets form a predetermined image on a recording surface. The capillary waves can be generated on the free surface of the liquid by using acoustical energy at a level approaching the onset of droplet ejection. The liquid used with the invention must also must be attracted by an electric field.
U.S. Pat. No. 5,006,170 (Schwarz et al.) and U.S. Pat. No. 5,122,187 (Schwarz et al.), the disclosures of each of which are totally incorporated herein by reference, disclose hot melt ink compositions suitable for ink jet printing which comprise a colorant, a binder, and a propellant selected from the group consisting of hydrazine; cyclic amines; ureas; carboxylic acids; sulfonic acids; aldehydes; ketones; hydrocarbons; esters; phenols; amides; imides; halocarbons; urethanes; ethers; sulfones; sulfamides, sulfonamindes; phosphites; phosphonates; phosphates; alkyl sulfines; alkyl acetates, and sulfur dioxide. Also disclosed are hot melt ink compositions suitable for ink jet printing which comprise a colorant, a propellant, and a binder selected from the group consisting of rosin esters; polyamides; dimer acid amides, fatty acid amides; epoxy resins; fluid paraffin waxes; fluid microcrystalline waxes; Fischer-Tropsch waxes; polyvinyl alcohol resins; polyols; cellulose esters; cellulose ethers; polyvinyl pyridine resins; fatty acids; fatty acid esters; poly sulfonamides; benzoate esters; long chain alcohols; phthalate plasticizers; citrate plasticizers; maleate plasticizers; sulfones; polyvinyl pyrrolidinone copolymers; polyvinyl pyrrolidone/polyvinyl acetate copolymers; novalac resins; natural product waxes; mixtures of linear primary alcohols and linear long chain amides; and mixtures of linear primary alcohols and fatty acid amides. In one embodiment, the binder comprises a liquid crystalline material.
“Reversible Polymers Formed from Self-Complementary Monomers Using Quadruple Hydrogen Bonding,” R. P. Sijbesma et al., Science, Vol. 278, p. 1601 (1997), the disclosure of which is totally incorporated herein by reference, discloses the use of units of 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds as the associating end group in reversible self-assembling polymer systems. The unidirectional design of the binding sites prevented uncontrolled multidirectional association or gelation. Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over lifetime and bond strength made many properties, such as viscosity, chain length, and composition, tunable in a way not accessible to traditional polymers. Hence, polymer networks with thermodynamically controlled architectures could be formed for use in, for example, coatings and hot melts, where a reversible, strongly temperature-dependent rheology is highly advantageous.
“Supramolecular Polymers,” R. Dagani, Chemical and Engineering News, p. 4 (December 1997), the disclosure of which is totally incorporated herein by reference, discloses self-assembling polymers containing the 2-ureido-4-pyrimidone group.
“Supramolecular Polymers from Linear Telechelic Siloxanes with Quadruple-Hydrogen-Bonded Units,” J. H. K. Hirschberg et al., Macromolecules, Vol. 32, p. 2696 (1999), the disclosure of which is totally incorporated herein by reference, discloses the preparation of telechelic oligo- and poly(dimethylsiloxanes) with two ureidopyrimidone functional groups by a hydrosilylation reaction. The compounds were characterized in solution by 1H NMR and viscometry and in the solid state by 1H NMR and 13C NMR, FTIR, and rheology measurements. The measurements showed that the ureidopyrimidone groups were associated via quadruple hydrogen bonds in a donor-donor-acceptor-acceptor array. In many aspects, the materials behaved like entangled, high molecular weight polymers.
“Design and Synthesis of ‘Smart’ Supramolecular Liquid Crystalline Polymers via Hydrogen-Bond Associations,” A. C. Griffin et al., PMSE Proceedings, Vol. 72, p. 172 (1995), the disclosure of which is totally incorporated herein by reference, discloses the creation of novel liquid crystalline materials by associating two complementary components through hydrogen bonding.
“The Design of Organic Gelators: Solution and Solid State Properties of a Family of Bis-Ureas,” Andrew J. Carr et al., Tetrahedron Letters, Vol. 39, p. 7447 (1998), the disclosure of which is totally incorporated herein by reference, discloses the synthesis of a family of bis-ureas that were shown to function as effective gelators in certain organic solvents. The X-ray structure of one bis-urea showed a cylindrical hydrogen bonding network with extensive interdigitation of the alkyl esters which project from the central rod.
“Hydrogen-Bonded Supramolecular Polymer Networks,” Ronald F. M. Lange et al., Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 37, p. 3657 (1999), the disclosure of which is totally incorporated herein by reference, discloses reversible polymer networks obtained by the strong dimerizing, quadruple hydrogen-bonding ureido-pyrimidone unit. A new synthetic route from commercially available starting materials is also described. The hydrogen-bonding ureido-pyrimidone network is prepared using 3(4)-isocyanatomethyl-1-methylcyclohexyl-isocyanate (IMCI) in the regioselective coupling reaction of multi-hydroxy functionalized polymers with isocytosines. 1H- and 13C-NMR, IR, MS, and ES-MS analysis, performed on a model reaction using butanol, demonstrated the formation of the hydrogen-bonding ureido-pyrimidone unit in a yield of more than 95 percent. The well-defined, strong hydrogen-bonding ureido-pyrimidone network was compared with a traditional covalently bonded polymer network, a multi-directional hydrogen-bonded polymer network based on urea units, and a reference compound. The advantage of the reversible, hydrogen-bonded polymer networks was the formation of the thermodynamically most favorable products, which showed a higher “virtual” molecular weight and shear modulus, compared to the irreversible, covalently bonded polymer network. The properties of the ureido-pyrimidone network were unique; the well-defined and strong dimerization of the ureido-pyrimidone unit did not require any additional stabilization such as crystallization or other kinds of phase separation, and displayed a well-defined viscoelastic transition. The ureido-pyrimidone dimerization was strong enough to construct supramolecular materials possessing acceptable mechanical properties.
“Combining Self-Assembly and Self-Association—Towards Columnar Supramolecular Structures in Solution and in Liquid-Crystalline Mesophase,” Arno Kraft et al., Polym. Mater. Sci. Eng., Vol. 80, p. 18 (1999), the disclosure of which is totally incorporated herein by reference, discloses the investigation of acid-base complexes that associate through hydrogen-bonding.
“Facile Synthesis of β-Keto Esters from Methyl Acetoacetate and Acid Chloride: The Barium Oxide/Methanol System,” Y. Yuasa et al., Organic Process Research and Development, Vol. 2, p. 412 (1998), the disclosure of which is totally incorporated herein by reference, discloses the synthesis of β-keto esters in good yield by reacting methyl acetoacetate with barium oxide, acylating the resulting barium complex with acid chloride, and then cleaving the α-acyl β-keto ester with methanol at a mild temperature. Using this procedure, various β-keto esters were prepared, such as methyl 4-phenyl-3-oxobutanoate, methyl 3-phenyl-3-oxopropionate, methyl 4-cyclohexyl-3-oxobutanoate, and methyl 3-oxooctadecanoate.
“Self-Complementary Hydrogen Bonding of 1,1′-Bicyclohexylidene-4,4′-dione Dioxime. Formation of a Non-Covalent Polymer,” F. Hoogesteger et al., Tetrahedron, Vol. 52, No. 5, p. 1773 (1996), the disclosure of which is totally incorporated herein by reference, discloses that 1,1′-bicyclohexylidene-4,4′-dione dioxime self-assembles into a non-covalent polymer structure in the solid state due to intermolecular directional hydrogen bonding between the oxime functionalities.
“Molecular Tectonics. Three-Dimensional Organic Networks with Zeolite Properties,” X. Wang et al., J. Am. Chem. Soc., Vol. 116, p. 12119 (1994), the disclosure of which is totally incorporated herein by reference, discloses molecules whose interactions are dominated by specific attractive forces that induce the assembly of aggregates with controlled geometries.
“Helical Self-Assembled Polymers from Cooperative Stacking of Hydrogen-Bonded Pairs,” J. H. K. Ky Hirschberg et al., Nature, Vol. 407, p. 167 (2000), the disclosure of which is totally incorporated herein by reference, discloses a general strategy for the design of functionalized monomer units and their association in either water or alkanes into non-covalently linked polymeric structures with controlled helicity and chain length. The monomers consist of bifunctionalized ureidotriazine units connected by a spacer and carrying solubilizing chains at the periphery. This design allows for dimerization through self-complementary quadruple hydrogen bonding between the units and solvophobically induced stacking of the dimers into columnar polymeric architectures, whose structure and helicity can be adjusted by tuning the nature of the solubilizing side chains.
“New Supramolecular Arrays based on Interactions between Carboxylate and Urea Groups: Solid-State and Solution Behavior,” Abdullah Zafar et al., New J. Chem., 1998, 137-141, the disclosure of which is totally incorporated herein by reference, discloses interaction between urea and carboxylate groups which can give extended hydrogen bonded aggregates.
U.S. Pat. No. 5,180,425 (Matrick et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink for ink jet printers which comprises an aqueous carrier medium, pigment dispersion or dye, and a polyol/alkylene oxide condensate cosolvent which eliminates film formation on thermal ink jet resistor surfaces thereby eliminating non-uniformity in optical density. The cosolvent present at least 5 percent has a solubility in water of at least 4.5 parts in 100 parts of water at 25° C. and a general formula: wherein X=—H or —CH3, R=—H, —CH3, —C2H5, —C3H7, —C4H9, or —CH2O(CH2CH2O)eH, b=0 or 1, a+d+f(c+e)=2 to 100; and f=1 to 6, the cosolvent being present in the amount of at least 4.5 percent based on the total weight of the ink jet ink composition. These inks exhibit freedom from thermal resistor film formation, have excellent decap performance, are storage stable and give images having excellent print quality.
While known compositions and processes are suitable for their intended purposes, a need remains for phase change inks that are suitable for hot melt ink jet printing processes, such as hot melt piezoelectric ink jet printing processes and the like. In addition, a need remains for phase change inks that are suitable for hot melt acoustic ink jet printing processes. Further, a need remains for phase change inks that generate images with reduction in waxy texture and feel. Additionally, a need remains for phase change inks that generate images with improved rub resistance. There is also a need for phase change inks that generate images with improved smear resistance. In addition, there is a need for phase change inks with desirably low viscosity values at the jetting temperature of a hot melt ink jet printer. Further, there is a need for nonaqueous phase change inks wherein water-soluble dyes can be selected as colorants.